This invention relates to inflatable boats, and more particularly to such craft capable of being driven at high speeds by an engine such as an outboard motor.
A wide variety of collapsible and inflatable boats have been known for thier virtues of compact storage when not in use, lightness in weight, and large measure of buoyancy. Those virtues have made such craft suitable for use as life boats, work boats that can be carried to places of use under circumstances that would be difficult to transport rigid boats, and for a variety of recreational uses.
One of the limitations characteristic of inflatable boats has been that the powering thereof by outboard motors of sufficient size to achieve planning speeds has met with only limited success. This is generally due to the inherently flexible nature of the craft, and particularly of the bottom or floor thereof which has a tendency to conform to the shape of the wave generated by the hull during movement through the water.
U.S. Pat. No. 4,251,893 discloses an inflatable boat, especially, suited for high speed use, wherein the floor structure or hull bottom comprises two superimposed upper and lower mat-like inflatable floors that, together with a rigid keelson, provide adequate rigidity for high speed planing operation without the need for floor boards for adding stiffness. The upper and lower inflatable floors or mats each comprise spaced top and bottom fabric walls that are interconnected by a multiplicity of flexible threads or drop-stitches of uniform length that serve as tension members to limit the spacing between the top and bottom walls when air is contained therebetween at greater than atmospheric pressure.
The exposed top and bottom farbric walls of each inflatable floor or mat have been built-up of multiple layers including an inner scrim layer to which the drop-stitches are attached, a first solid sealer adhesive layer, a lightweight chafer layer of nylon or other woven synthetic fabric that is coated and impregnated with a rubber or rubber-like material such as neoprene, a second solid sealer adhesive layer, and a heavy duty chafer layer of synthetic fiber fabric coated and/or impregnated with rubber or synthetic rubber material.
That construction has been subject to the formation of air blisters between the inner lightweight rubberized fabric layer and the outer, heavy duty, wear and scuff resistant rubberized layer. These blisters are formed by otherwise insignificant permeation of inflating air passing outwardly through the inner layer of sealing material, and trapped by the second layer of sealing material and/or the heavy duty chafer layer. The air blister formation is characterized by partial separation of layers and the appearance of substantial bulges in the exposed surfaces of the floor. These blisters are not only unsightly but also, when occurring on the hull bottom, impair waterflow and the high speed planing characteristics of the boat.